The study of elastic properties of solids is essential to both physics and engineering. Finding simple, easy-to-visualize examples to demonstrate these concepts is often difficult. In a previous article written by one of us (KAPII), a simple method for determining Youngs modulus using marshmallows was given.1 In this article we will illustrate another method to explore elastic properties of everyday materials. This experiment uses a common plastic spoon exposed to a transverse force in order to determine the stiffness constant, yield point, and rupture point of the plastic spoon. In addition, much like the “Youngs Modulus of a Marshmallow” activity, this experiment visually demonstrates Hooke's law, is fun and easy to perform, and leaves a lasting impression on the students.
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The finite element model shown in Fig. 3 was created using FEMAP with NX Nastran by Cori Warren and modified by Jill M. Pestka, used with permission.
In order to fully describe the complex bending behavior of the spoon, Hooke's law must be extended to three dimensions. In this case both Young's modulus and the shear modulus are required in such a model due to the presence of shear, tensile, and compressive motion in the system. Also, the structural characteristic of the spoon (the shape of the shaft and cup) strongly influence its behavior. Thus, while the given experiment produces excellent results for the one-dimensional stiffness constant, the finite element model incorporates all of these properties in order to reproduce the overall behavior of the spoon.
